Dynamic Scheduling Cell Switching for TDD Carrier Aggregation
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Solution Overview
Problem
In wireless communication systems, CA-capable UEs configured with multiple TDD cells having different UL-DL configurations face issues with no PDCCH for DL resource allocation and HARQ ACK/NACK feedback timing, leading to incomplete bandwidth utilization and re-transmissions.
Innovation Solution
Configuring at least two scheduling cells to provide downlink control signalling, including DL and UL grant resource assignments, HARQ ACK/NACK feedbacks, synchronization channels, and system information, allowing flexible allocation and synchronization across multiple cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If cross-carrier scheduling is configured with a single scheduling cell, then PDCCH channel interference is reduced, but DL resource allocation fails when the scheduling cell's subframe is a UL subframe
Solution Approach 1:
The system dynamically changes the scheduling cell parameter based on subframe type. When the primary scheduling cell is in a UL subframe, the system switches to an alternative scheduling cell in a DL subframe, ensuring continuous DL resource allocation capability while maintaining interference reduction benefits
Solution Approach 2:
An alternative scheduling cell acts as an intermediary when the primary scheduling cell cannot provide DL resource allocation. This intermediary cell ensures that DL resources can still be allocated even when the primary scheduling cell's subframe is designated for UL transmission
2Device complexity
If a single scheduling cell is used for cross-carrier scheduling, then system complexity is reduced, but HARQ ACK/NACK feedback timing cannot be satisfied when subframe alignment fails
Solution Approach 1:
The system dynamically adjusts the scheduling cell configuration based on TDD UL-DL configuration alignment. When subframe alignment fails and HARQ timing cannot be satisfied, the system switches to an alternative scheduling cell that has proper alignment, ensuring reliable HARQ feedback timing without permanent complex configuration
Solution Approach 2:
The scheduling cell configuration is made dynamic rather than static. The system can switch between primary and alternative scheduling cells based on real-time subframe alignment conditions, allowing the system to adapt to different TDD configurations and maintain HARQ timing requirements
3Productivity
If carrier aggregation is configured with multiple cells having different TDD UL-DL configurations, then bandwidth utilization is improved, but PDCCH availability becomes inconsistent across cells
Solution Approach 1:
An alternative scheduling cell serves as a mediator when the primary scheduling cell cannot provide PDCCH in a given subframe. This ensures that control signaling is always available for DL resource allocation across cells with different TDD configurations, maintaining PDCCH availability consistency
Solution Approach 2:
The system changes the active scheduling cell parameter based on PDCCH availability in different subframes. When the primary scheduling cell's subframe is a UL subframe, the system switches to an alternative scheduling cell, ensuring continuous PDCCH availability while maintaining the benefits of multi-cell carrier aggregation
Data Source
AI summary
A method and a wireless communication system for providing downlink (DL) control signalling for a communication apparatus are provided. In the method, at least two scheduling cells are configured for providing DL control signalling, and the DL control signalling is provided on one or more of the at least two scheduling cells for a scheduled cell.